The invention relates to an exposure control method in which, when exposure data is determined in a picture printing device or a picture processing device such as a photographing camera, especially an 8-mm movie camera or a VTR camera, exposure data for a particular scene is determined utilizing the exposure data of several scenes before and after that scene.
When similar or continuous scenes are reproduced the reproduced scenes generally have the same density and color. Similar scenes, in general, differ from one another in details such as camera angle, background and the size and position of a photographed main object. However, if the exposure data of a scene is determined according to an exposure calculating expression using the maximum and minimum values of the photometric values of the similar scenes and the exposure data of a position on a main object (for instance the average photometric value of the central part of the main object), unlike the case where the exposure data is determined using an average characteristic value such as a large area average photometric value, if the scenes differ even slightly, the aforementioned exposure controlling characteristic values are greatly affected. As a result, the similar scenes are reproduced with non-uniform density and color.
This is a serious problem for a picture printing device, a photographing camera, etc. Usually, the prints of similar scenes provided by a picture printing device are arranged side-by-side in an album. If the picture thus arranged were to be observed separately, no differences would be immediately apparent. However, observed together the differences in density and color will be readily perceptible. Especially for an 8-mm camera or a VTR camera, it is desirable that similar, continuous scenes be reproduced as uniform in density and color as possible because pictures of such similar, continuous scenes, which are to be viewed in close sequence, are often taken by these cameras.
Examples of a conventional similar scene picture printing exposure data control method for a picture printing device have been disclosed in Japanese Laid-Open Patent Application Nos. 40942/1974 and 112345/1976. In the method of the former, the full-area transmission densities of several frames before and after a particular frame to be printed and/or the printing exposure data of frames which are regarded as equivalent in photographical optical quality as compared with the printing exposure data of the frame to be printed to determine correction data which is applied to the frame. In the method of the latter, the color balance is controlled as a function of both the average characteristic value of a group of frames and the characteristic value of the frame to be printed. Thus, in each of the conventional methods, the average value of the exposure data of a plurality of frames which are determined as similar scenes and the value of the exposure data of frame to be printed are employed. However, the conventional methods still involve a drawback. That is, in the conventional methods, the scenes are classified into two groups wherein in one group the scenes are similar and in the other group the scenes are not similar. The average value of the exposure controlling characteristic values of a plurality of original pictures which are determined as similar scenes is utilized. Accordingly, it is necessary to determine whether the scenes are similar to one another or not. The result of the determination greatly affects the exposure data control. In other words, the exposure data when scenes are determined as being similar is considerably different from the exposure data when the scenes are determined as not being similar. Thus, the conventional methods involve a serious drawback in that, if the determination is erroneous, then not only an exposure control is erroneously applied to a particular original picture, but also the exposure control of all of the original pictures from which the erroneous determination has been made is carried out erroneously.